It is known how to provide a permanently installed roll bar spanning the entire width of the vehicle. In this solution, the increased air drag and the occurrence of driving noises is perceived as a drawback, apart from affecting the appearance of the vehicle.
It is also known how to coordinate a permanently installed, i.e., rigid U-shaped roll bar of unchangeable height with each vehicle seat. This solution is typically used in sports cars to underscore the sporty appearance.
Widely used in convertibles are structural solutions in which the U-shaped roll bar is retracted in the normal condition, and in case of danger, i.e., an imminent rollover, it is quickly extended into a protecting position, in order to prevent the passengers from being crushed by the vehicle rolling over.
These rollover protection systems typically have a U-shaped roll bar arranged in a guide body fixed to the vehicle, or a roll bar formed from a profile body, while the guide body is secured in a case housing. This roll bar or roll body in the normal state is held down in a position of rest by a holding device against the pre-stress force of an activating compression spring, and in event of a rollover a sensor releases the holding device and the force of the compression spring brings it into an upper protecting position, while a locking device which is then activated prevents the roll bar from being retracted or pushed in. Typically one case is assigned to each vehicle seat, especially for the rear seats. Alternatively, two cases can also be integrated in a rear wall structural unit.
One such case design for a roll bar system with a U-shaped roll bar is shown by DE 43 42 400 A 1.
The invention starts both from over-roll protection systems with rigidly installed roll bar and also those with deployable U-shaped roll bar, yet it also comprises systems in which only the top piece of the roll bar, formed from a profiled body, for example, is rounded in a U-shape.
U-shaped roll bars are today typically fabricated from simple pipe bending parts, with a rounded top piece and two parallel leg pieces. Such a U-shaped roll bar can be bent into a U-shape from a single piece of steel or aluminum tubing, or it can consist of a tubular and U-shaped top piece, to which the leg tubes are welded. In such a three-piece roll bar, the top piece can also be connected to the leg tubes by screwing, gluing, or a form-fitted connection (e.g., DE 202 15 276 U1). The U-shaped top piece can advantageously be made from a different material than the leg tubes.
U-shaped roll bars, and especially rigid roll bars, which are permanently arranged to be visible in the vehicle, are subject increasingly to safety engineering and also design-oriented requirements. The result is roll bars which, due to the necessary shape, and necessary length and cross section, are no longer fabricated as simple pipe bending parts. These requirements demand a three-dimensional bar contour with irregular cross section of the bar profile. As part of the safety engineering, there can be greatly rounded and flattened segments near the head of the vehicle passengers, so as to minimize the severity of an injury by the thickest possible foam padding.